let m = new Map()
m.set('first',1)
m.set('second',2)
m.set('third',3)
console.log(m)
m.forEach((x,y) =>{
    console.log('key: '+x+'  value: '+y)
})
for(let key of m.keys()){
    console.log('keys: '+key);
}
for(let value of m.values()){
    console.log('value: '+value);
}
console.log(m.has('first'));
